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read-cache: speed up add_index_entry during checkout

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Teach add_index_entry_with_check() and has_dir_name()
to see if the path of the new item is greater than the
last path in the index array before attempting to search
for it.

This is a performance optimization.

During checkout, merge_working_tree() populates the new
index in sorted order, so this change saves at least 2
lookups per file.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
This commit is contained in:
Jeff Hostetler
2016-12-06 16:33:39 -05:00
committed by Johannes Schindelin
parent d5251c7b08
commit 4e6cb0e08b
2 changed files with 72 additions and 1 deletions
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1
cache.h
View File

@@ -572,6 +572,7 @@ extern int write_locked_index(struct index_state *, struct lock_file *lock, unsi
extern int discard_index(struct index_state *);
extern int unmerged_index(const struct index_state *);
extern int verify_path(const char *path);
extern int strcmp_offset(const char *s1_in, const char *s2_in, int *first_change);
extern int index_dir_exists(struct index_state *istate, const char *name, int namelen);
extern void adjust_dirname_case(struct index_state *istate, char *name);
extern struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int igncase);

72
read-cache.c
View File

@@ -894,6 +894,34 @@ static int has_file_name(struct index_state *istate,
return retval;
}
/*
* Like strcmp(), but also return the offset of the first change.
*/
int strcmp_offset(const char *s1_in, const char *s2_in, int *first_change)
{
const unsigned char *s1 = (const unsigned char *)s1_in;
const unsigned char *s2 = (const unsigned char *)s2_in;
int diff = 0;
int k;
*first_change = 0;
for (k=0; s1[k]; k++)
if ((diff = (s1[k] - s2[k])))
goto found_it;
if (!s2[k])
return 0;
diff = -1;
found_it:
*first_change = k;
if (diff > 0)
return 1;
else if (diff < 0)
return -1;
else
return 0;
}
/*
* Do we have another file with a pathname that is a proper
* subset of the name we're trying to add?
@@ -905,6 +933,21 @@ static int has_dir_name(struct index_state *istate,
int stage = ce_stage(ce);
const char *name = ce->name;
const char *slash = name + ce_namelen(ce);
int len_eq_last;
int cmp_last = 0;
if (istate->cache_nr > 0) {
/*
* Compare the entry's full path with the last path in the index.
* If it sorts AFTER the last entry in the index and they have no
* common prefix, then there cannot be any F/D name conflicts.
*/
cmp_last = strcmp_offset(name,
istate->cache[istate->cache_nr-1]->name,
&len_eq_last);
if (cmp_last > 0 && len_eq_last == 0)
return retval;
}
for (;;) {
int len;
@@ -917,6 +960,24 @@ static int has_dir_name(struct index_state *istate,
}
len = slash - name;
if (cmp_last > 0) {
/*
* If this part of the directory prefix (including the trailing
* slash) already appears in the path of the last entry in the
* index, then we cannot also have a file with this prefix (or
* any parent directory prefix).
*/
if (len+1 <= len_eq_last)
return retval;
/*
* If this part of the directory prefix (excluding the trailing
* slash) is longer than the known equal portions, then this part
* of the prefix cannot collide with a file. Go on to the parent.
*/
if (len > len_eq_last)
continue;
}
pos = index_name_stage_pos(istate, name, len, stage);
if (pos >= 0) {
/*
@@ -1008,7 +1069,16 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
if (!(option & ADD_CACHE_KEEP_CACHE_TREE))
cache_tree_invalidate_path(istate, ce->name);
pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce));
/*
* If this entry's path sorts after the last entry in the index,
* we can avoid searching for it.
*/
if (istate->cache_nr > 0 &&
strcmp(ce->name, istate->cache[istate->cache_nr - 1]->name) > 0)
pos = -istate->cache_nr - 1;
else
pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce));
/* existing match? Just replace it. */
if (pos >= 0) {